I'm not saying it's a "death sentence", just that physically, your body tends to deteriorate with age. The situation isn't a binary one: being young, your body is much more forgiving, which eases parenting, especially if you want to have more than one child.

So yeah, it's better to start having children early than late. It doesn't mean that you'll be crippled in bed because you had them late (aside from the fertility issues).

Also, Hacker News is essentially composed of well-off, western people working in white collar jobs. Of course, those people will have easy and healthy lives; I wouldn't say the same for a mason or a cashier, and those people exist.